1. Field of the Invention
The present invention relates to a memory control apparatus and, more particularly to, a memory control apparatus, which is suitably used in, e.g., control of I/O processing of a waveform data memory for storing waveform data, in a tone generator of an electronic musical instrument.
2. Description of the Related Art
Conventionally, a tone generator system of a so-called PCM tone generation type, which sequentially reads out waveform data stored in a waveform memory at a predetermined sampling period, and generates tones based on the readout data, is known. Normally, a tone generator system has a plurality of channels, and time-divisionally executes processing of the channels. For example, a predetermined period of time is equally divided by the number of channels, and a series of processing operations of the channels are performed such that waveform data of the first channel is read out in a first time-slot interval, waveform data of the second channel is read out in a second time-slot interval, . . . . Such processing is repeated to sequentially read out waveform data, thereby generating tones.
The write operation of waveform data in the waveform memory is separately executed. More specifically, the operation of the tone generator is temporarily stopped, and waveform data sent from another unit (e.g., waveform data obtained by sampling external tones inputted from a microphone, waveform data pre-stored in a hard disk, and the like) are written in the waveform memory. During execution of the write operation of waveform data, the tone generator cannot perform tone generation. Therefore, since the tone generation based on waveform data read out from the waveform memory cannot be executed parallel to the write operation into the waveform memory, this tone generator system cannot record/reproduce waveform data beyond the memory capacity.
In order to allow the write operation parallel to the read operation from the waveform memory, a certain system assigns some of the plurality of channels to recording channels. With this system, waveform data from, e.g., a hard disk can be written in the waveform memory while reading out waveform data from the waveform memory. Therefore, waveform data beyond the memory capacity of the waveform memory can be recorded/reproduced.
However, when some of channels are assigned to recording channels, the number of channels used for tone generation is decreased. Furthermore, when the number of channels used for transferring waveform data from, e.g., a hard disk is small, the transfer time is prolonged.